Terms, spectroscopic

Table 18.4 Energies of Spectroscopic Terms for Gaseous d2 Ions. ...

Each separate energy level is given a label called a (spectroscopic) term symbol. For the moment it is sufficient to regard these merely as labels. See Further Reading at the end of this chapter for mote information. 

The subshells are labelled s, p, d and f. These letters originally came from old spectroscopic terms sharp , principal , diffuse and fundamental , but these terms are no longer important. 

The energy level values of the lowest spectroscopic term of the electronic configuration of lanthanide as well as actinide atoms, were tabulated by Brewer. Such tables are very useful for phenomenological correlations concerning actinide metals (see Chap. C). From these tables one can obtain Table 1 giving the ground state and the first excited level of the actinide atoms as well as of the lanthanide atoms for comparison ... 

The spectroscopic term symbols for the molecular case can be obtained,... 

Spectroscopic terms arising from equivalent electronic configurations in L-S coupling... 

The formation of a coordinated reduced nitrobenzoato ligand radical (or, in spectroscopic terms, a MLCT excited state) has been found in the reaction of e-q with pentaaminocobalt(III) complexes containing a mono- or di-nitrobenzoato ligand272. Such a coordinated radical disappears via unimolecular kinetics, which represents ligand-to-metal intramolecular electron transfer with formation of Co2+... 

Equation (33) means also that spectroscopic terms (energy levels) can be assigned to the product functions and the transitions defined between them have well determined energies (Figure 6). These transitions define the precession frequency of the corresponding single quantum coherences. 

Many-electron atoms electronic configuration and spectroscopic terms... 

Spectroscopic terms arising from a given electronic configuration... 

We are now in position to derive the electronic states arising from a given electronic configuration. These states have many names spectroscopic terms (or states), term symbols, and Russell-Saunders terms, in honor of spectroscopists H. N. Russell and F. A. Saunders. Hence, the scheme we use to derive these states is called Russell-Saunders coupling. It is also simply referred to as L-S coupling. 

Table 2.3,2. Spectroscopic terms arising from configurations sn, pn, and dn...

As shown in previous sections, under an octahedral crystal field, the five d orbitals are split into two sets of orbitals, /2g and eg. In terms of spectroscopic states, we can readily see that the 2D term arising from configuration d1 will split into 2r2g and 2E% states, arising from configurations t g and e, respectively. But what about the spectroscopic terms such as F and G arising from other d" configurations In this section, we will see how these terms split in an octahedral crystal field. 

To see how an octahedral crystal field reduces the (2L+l)-fold degeneracy of a spectroscopic term, we first need to determine the character of a rotation operating on an atomic state defined by the orbital angular momentum quantum number L. It can be shown that the character / for a rotation of angle a about the z axis is simply... 

After determining what levels are present for an octahedral complex with a given electronic configuration, we are now ready to discuss the energy level diagrams for these spectroscopic terms. 

Tanabe-Sugano diagrams for d2, d3. and d8 octahedral complexes. Quantities B and C are Racah parameters, in terms of which the energy of a spectroscopic term is expressed. Hence both EIB and Dq/B are dimensionless. 

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